Key Lessons for Hot Work Safety from US CSB

Posted on 9/30/2022 by Roger Marks

Following the investigation of a flash fire and explosion incident at a crude oil terminal in Texas, the Chemical Safety and Hazard Investigation Board (CSB) has issued a report that includes key safety recommendations for hot work.

The incident occurred in 2016, while contractor employees were welding a section of piping that contained residual crude oil.

The residual oil inside the pipe created an explosive atmosphere. When exposed to an ignition source (i.e., a welding torch), the residual crude oil ignited, causing a flash fire and explosion that injured seven workers.

The section of piping was cut and isolated before “hot work” started. However, it was not cleared of flammable material or made inert.

What is “Hot Work”?

Hot work refers to a process or activity that involves a flame, heat, or production of sparks. Jobs like welding, open-flame soldering, brazing, and arc cutting are considered hot work (NFPA Fact Sheet). See also: OSHA’s definition of hot work in 29 CFR 1917.152(a)

Hot work can start a fire or cause an explosion. It is especially dangerous when flammable or combustible materials are present.

The OSHA general industry regulations for welding, cutting, and brazing (29 CFR 1910, Subpart Q) prohibit cutting or welding “in the presence of explosive atmospheres (mixtures of flammable gases, vapors, liquids).”

In addition, NFPA Standard 51B states that cutting or welding shall not be permitted in the presence of explosive atmospheres that may develop inside uncleared or improperly prepared tanks or equipment that previously contained flammable material.

OSHA incorporates this NFPA Standard by reference in 29 CFR 1910.6. OSHA’s construction and maritime industry standards also include specific requirements for hot work to prevent a fire or explosion (see 29 CFR 1926.352 and 1917.152).

NFPA Fact Sheet: Hot Work Safety

Key Lessons for Hot Work Safety from US CSB

CSB’s 3 Key Lessons

CSB urges companies to take away three key lessons from the 2016 incident, which are found in section 4 of the Board’s final report.

When hot work will be performed, employees should ensure that the internal atmosphere in the pipe or equipment is not flammable. To mitigate the risk of fire/explosion, equipment can be cleaned, purged with inert gas like nitrogen, or filled with water before hot work is performed.

Secondly, zones where hot work will be performed must be assessed to identify any flammable or combustible vapors, liquids, or other materials that are nearby. A “robust mitigation plan to prevent fires and explosions” should be developed.

Third, CSB reiterates some key to preventing hot work incidents that were stressed in a 2010 Safety Bulletin and a Fact Sheet. Among these are finding alternatives to hot work, monitoring and testing the atmosphere/area where work will be performed, using written permits, providing thorough employee training, and adequately supervising contractors.

The full Final Report from, CSB is available here.

Tags: combustibles, flammables, hot work, safety, tips, workplace

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